Brake lathes for truing brake rotors have long been known in the art. Generally, in these devices, a rotor is mounted upon an arbor so that the arbor and rotor may be rotated together about a common axis by an alternating current motor. A tool holder is provided for holding cutting tools in working engagement with a braking surface of the rotor. The tool holder is mounted upon a track which allows it to move translationally to draw the cutting tool progressively across the braking surface of the rotor as the rotor rotates with the arbor during a truing operation. In devices of the prior art, movement of the tool holder has been accomplished by a mechanical drive, such as a worm drive, which is linked to the arbor and alternating current motor by a drive train which may include gears, clutches and the like. While these devices of the prior art have provided for selection of the rate of progression of the cutting tool across the rotor surface by changing gear ratios in the drive train between the arbor drive tool holder drive, the selection of cutting rate has been limited to a small number of fixed rates corresponding to the specific gear ratio combinations made available within the drive train. The gear pairs and clutches of these drive trains of the prior art lathes produce vibration and noise and transmit noise from the arbor to the tool drive which increases the difficulty of achieving a satisfactorily smooth surface during the truing process. In recent years, brake rotors have been made of increasingly diverse materials, making it necessary to provide many different tool progression cutting rates if a lathe is to achieve an acceptable finish on the braking surface of all commercially available rotor products.